Mechanical Circulatory Support And Heparin-Induced Thrombosis

Heparin remains the "gold standard" anticoagulant in cardiac surgery. However this extract from pork intestinal mucosa has an antidote of foreign structure (salmon semen) and is far from an ideal drug.

The interaction with platelets is more complex than with other antithrombotics.

Heparin induced thrombocytopenia is rare but occurs at a frequency which is not low because of massive use.

0,5% of treatments by LMWH
1% of treatments by UFH
3% of treatments by UFH during cardiac surgery
5% of treatments by UFH during orthopedic surgery
10% of treatments by UFH during circulatory support

In 50 % of the cases of HIT paradoxal thrombosis occur under well-conducted treatment by heparin in veins and arteries (pulmonary embolism, myocardial infarction, cerebro-vascular accident, phlebitis, adrenal necrosis...)

An other particularism is the hypercoagulable state which is seen despite thrombopenia and which requires aggressive treatment (bolus).

Among 35 cases of biventricular assistance with Thoratec® and 2 cases with Medos® we observed 3 cases of HIT.

1st A... 50 years old ischemic cardiomyopathy
2nd K... 44 years old ischemic cardiomyopathy
3rd L... 51 years old ischemic cardiomyopathy

The platelet count falls after the 5th day of treatment with heparin UFH and rises after suspension of all types of heparin administration.

The presence of anti-heparin – PF4 complex antibodies is demonstrated by ELISA-test which is strongly positive (OD more than 1).

Moreover A... suffered from transitory aphasia under Thoratec® K... presented left hemiplegia under cardiac assistance and presented a splenic rupture.

L... was unfortunately transplanted under heparin UFH and presented myocardial infarction with a white clot in left main coronary artery.

The arguments for HIT are strong but can be discussed.

- 40 % of positive ELISA test after CPB without HIT (sometimes with OD more than)
- Thrombocytopenia may be due to dilution, sepsis, post-transfusion, CPB, under-production...
- Frequency is surprisingly high but other teams point out the same phenomenon.

Schenk (Bad Oeynhausen) 10,6 % of 115 VAD patients (83,3 % of them experienced one or more thrombotic events).

Koster (Berlin) 7,8 % of 358 patients with 14,3 % having thrombosis.

Our serie is small but emphasizes the necessity of vigilance when using heparin :

- rigorous search for previous contacts with heparin
- building a curve for platelet cinetics
- examination for venous or arterial thrombosis
- anti-heparin-PF4 complex antibodies at high level
- positive platelet aggregation test in presence of UFH
- rising of platelet count after removal of UFH
- substitution of heparin by lepirudin, danaparoïd, argatrobon, bivalirudin, tirofiban, prostaglandin.
- No AVK treatment too early.

 
References:

• Schenk S, El-Banayosy A, Prohaska W, et al. Heparin-induced thrombocytopenia in patients receiving mechanical circulatory support. J Thorac Cardiovasc Surg 2006; 131 (6): 1373-81
• Koster A, Huebler S, Potapov E et al. Impact of heparin-induced thrombocytopenia on outcome in patients with ventricular assist device support : single institution experience in 358 consecutive patients. Ann Thorac Surg 2007;83:72-6
• WarkentinTE,CrowtherMA. When is HIT really HIT? Ann Thorac Surg 2007;83:21-3

Figure 1: Platelet count patient A

Figure 2: Platelet count patient K

Figure 3

CV of the author
- J. C. Thiranos in charge of the intensive care (12 beds) of the cardio-vascular surgical departement (1.000 cardiac operations under cardio-pulmonary bypass pro year) I am chief of ICU since 23 years

CV of the author
- Professor JP Mazzucotelli is the surgeon in charge of cardiac assistance programm

CV of the author
- Dr. M. Arguello was member of the surgical team.

CV of the author
- Dr. A. Zazu was member of the intensivist team. They returned to Argentina.

Publication: November 2007

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November 30th., 2007

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